module GraphQL::StaticValidation::FragmentsAreOnCompositeTypes

def on_fragment_definition(node, parent)
  validate_type_is_composite(node) && super
end

def on_inline_fragment(node, parent)
  validate_type_is_composite(node) && super
end

def validate_type_is_composite(node)
  node_type = node.type
  if node_type.nil?
    # Inline fragment on the same type
    true
  else
    type_name = node_type.to_query_string
    type_def = context.warden.get_type(type_name)
    if type_def.nil? || !type_def.kind.composite?
      add_error(GraphQL::StaticValidation::FragmentsAreOnCompositeTypesError.new(
        "Invalid fragment on type #{type_name} (must be Union, Interface or Object)",
        nodes: node,
        type: type_name
      ))
      false
    else
      true
    end
  end
end